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Biomedical subjects

H W Peter

Publications and source records attributed to H W Peter.

15 recordsLinked to original sources
PubMed1984

Membrane alterations in magnesium-deficiency-induced malignant T cell lymphoma.

Malignant T cell lymphoma cells induced in the thymus by chronic Mg deficiency showed a less ruffled surface in the scanning electron microscope, particularly after intraperitoneal transplantation. Their content of phosphatidylserine and phosphatidylinositol was increased. The content of phosphatidylcholine, cholesterol and the cholesterol/phospholipid ratio, and thus membrane microviscosity, were decreased. The activity of phospholipid methyltransferase I and II was reduced. In parallel to these alterations, 45Ca2+ influx and efflux as well as 45Ca2+ content in mitochondria, microsomes and cytosol of lymphoma cells were enhanced.

Animals↗
PubMed1981

Regulation of the F-ATPase from mitochondria of Vigna sinensis (L.) Savi cv. Pitiuba by spermine, spermidine, putrescine, Mg2+, Na+, and K+.

Mitochondria from Vigna sinensis (L.) Savi cv. Pitiuba contain the polyamines spermine, spermidine, and putrescine. The membrane-bound F1-ATPase from mitochondria of Vigna sinensis is activated by these polyamines at physiological concentrations. The effect of polyamines on the membrane-bound of F1-ATPase is dependent on the concentrations of Na+, K+, MgATP, and Mg2+. Excess Na+ or K+ prevents the activation of the membrane-bound F1-ATPase by spermine and spermidine, but not by putrescine. The most pronounced effects were observed at low MgATP concentrations in the absence of Na+ and K+. At [MgATP] = 0.08 mM, spermine activation of the membrane-bound F1-ATPase was 130%. The membrane-bound F1-ATPase is slightly activated by Mg2+ at lower concentrations and strongly inhibited by Mg2+ at higher concentrations. Activation as well as inhibition is dependent on the substrate MgATP concentration. Although there is competition between Mg2+ and MgATP, the binding sites for these two ligands are different (pseudocompetitive inhibition). The inhibition of the membrane-bound F1-ATPase can be reversed by polyamines. There is evidence that the binding sites for Mg2+ and polyamines are identical. The F1-ATPase detached from the membrane is neither activated by polyamines nor inhibited by Mg2+. Therefore, the binding sites for Mg2+ and polyamines seem to be localized on the membrane.

Adenosine Triphosphatases↗
PubMed1977

Inhibition of Na,K-ATPase from chick brain by polyamines.

The amounts of the polyamines putrescine, spermine and spermidine as well as the Na,K-ATPase activity have been determined in the developing chick brain. The amounts of spermine and spermidine per gram fresh weight do not change significantly, the amount of putrescine declines until the 17th day of incubation after which an increase takes place. Spermine is able to inhibit the Na,K-ATPase from chick brain competitively. Half maximal inhibition is achieved at 4 X 10(-5) mol/1 spermine. This polyamine functions as an allosteric inhibitor; the Hill coefficient is 2.2 +/- 0.3. A regulatory effect of spermine on the Na,K-ATPase from chick brain is discussed. In contrast to spermine 1 mmol/1 spermidine inhibits the Na,K-ATPase only slightly, while 1 mmol/1 putrescine does not inhibit the Na,K-ATPase at all.

Adenosine Triphosphatases↗
PubMedDate not supplied

Effects of phospholipids in the action of acetyl-CoA carboxylase from rat liver.

Acetyl-CoA carboxylase (E.C. 6.4.1.2) was isolated from rat liver. The purified enzyme contains phospholipids with a rather large amount of phosphatidylinositol (26%). Incubation of the purified acetyl-CoA carboxylase with phospholipase A2 (E.C. 3.1.1.4) or with phospholipase D (E.C. 3.1.1.4) diminishes the phospholipid content by 70%, this treatment leading to a complete inactivation of the enzyme. After removal of the phospholipases, the lipid-depleted enzyme can be reactivated to a certain degree by incubation with a phospholipid extract from rat liver, with phosphatidylinositol alone, or with serum albumin.

Acetyl-CoA Carboxylase↗